Wire wrapping apparatus

ABSTRACT

Apparatus for tightly wrapping wire on an angular terminal, said apparatus comprising an axially rotatable mandrel by means of which wire is fed onto the terminal which, during wrapping, is located in a coaxial recess in the mandrel, said recess having an internal wall which compresses the wire onto the terminal, wherein thrust ramp means is provided in the recess, said thrust ramp means being axially disposed from the feed point of the wire onto the terminal so that upon rotation of the mandrel relative to the terminal the thrust ramp means co-operates with the lastwrapped turn of wire on the terminal to produce axial movement of the mandrel relative to the terminal by a predetermined distance at least equal to the thickness of the wrapped wire per turn of the mandrel.

United States Patent Boothby Sept. 9, 1975 WIRE WRAPPING APPARATUS 3,781,932 1/1974 Baker et a1. 140/124 x 1 3,803,649 4 1974 Sk tt 1. 140 124 X [75] Inventor: Walter Evelyn Brooke Boothby, East u et a Stanmore, England FOREIGN PATENTS OR APPLICATIONS 73 Assignee: The Post Office London England 887,999 12/1971 Canada 140/124 [22] Filed: 1973 Primary ExaminerC. W. Lanham [21] A pl. No 387,296 Assistant Examiner-E. M. Combs Attorney, Agent, or F irmKemon, Palmer & E t b k 30 Foreign Application Priority Data s a mo .1197 UdK'd 4 Aug 5, 2 nlte mg om 3794 I72 [57] ABSTRACT [52] US. Cl. 140/124; 29/203 D; 242/7.17; Apparatus for tightly wrapping wire on an angular ter- 242/7.06 minal, said apparatus comprising an axially rotatable [51] Int. Cl. B21F 3/02; B21F 3/04; H01R 9/14 mandrel by means of which wire is fed-onto the termi- [58] Field of Search 29/203 D, 203 H, 203 HM; nal which, during wrapping, is located in a coaxial re- 140/1 17, 122, 124; 242/7.06, 7.17; 81/95 R; cess in the mandrel, said recess having an internal wall 7/14 1 R which compresses the wire onto the terminal, wherein thrust ramp means is provided in the recess, said [56] References Cited thrust ramp means being axially disposed from the UNITED STATES PATENTS feed point of the wire onto the terminal so that upon 2 746 124 5/1956 Belek 242/7 17 X rotation of the mandrel relative to the terminal the 2758797 8/1956 242'/7 17 thrust ramp means co-operates with the last-wrapped 2 926 859 3/1960 Bos et al...: 21:1. 242 7.17 mm of Wire on the terminal to P axial move- 310773211 2/1963 Brooks 242/7.06 mem 0f the mandrel relative to the terminal y a P 3,095,913 7/1963 Shepherd r al 242/7 06 determined distance at least equal to the thickness of 3,244,202 4/1966 Huang 140/124 the wrapped wire per turn of the mandrel. 3,531,056 9/1970 Baker et a]. 242/7.17 3,625,262 12 1971 Baker et al. 242/7.17 3 (31311115, 3 Drawlng Flgures t 1 28 1o 34 I PATENTEU SEP 91975 szmengz WIRE WRAPPING APPARATUS This invention relates to apparatus for making electrical connections by means of wrapped joints.

With some previously known apparatus for making wrapped joints, there has been a tendency for the wire to be overwrapped, that is for a turn of the wire to be laid on a preceding turn rather than directly onto the terminal. Apart from the consequent untidy appearance of the joint, over-wrapping can give rise to a number of problems, such as unacceptably high contact resistance and the risk of short circuits. More important, as it is necessary to wrap the wire very tightly, it would be possible for the wire to be severed if over-wrapped.

It is an object of the invention to provide means for wrapping the wire in serially disposed turns, thus to prevent over-wrapping.

It is known to make a wrapped joint on a terminal by means of a rotatable mandrel engaged with the terminal. The present invention provides thrust means on the mandrel which, during a rotation of the mandrel, cooperates with the last-wrapped turn of wire on the terminal to produce axial movement of the mandrel relative to the terminal by a predetermined distance at least equal to the diameter of the wrapped wire, so that overwrapping is avoided.

Thus, according to the invention there is provided apparatus for wrapping serially axially disposed turns of wire onto an axially extending terminal to make an electrical connection therewith, said apparatus comprising a wrapping mandrel rotatable in a first direction to wrap said wire and having a bore formed in a forward end thereof, the bore extending rearwardly to receive the terminal, a recess defined by a wall extending at least partly around said bore to compress wrapped wire onto the terminal and a wire feed aperture adja cent the bore, wherein the mandrel is formed with thrust means within said recess adapted to co-operate with a last-wrapped turn of wire on the terminal to progress the mandrel axially along the terminal as the mandrel is rotated to wrap the wire.

The simultaneous rotation and axial progression of the mandrel causes each point thereon to move in a substantially helical path and wire wrapped on a terminal using the apparatus will accordingly extend substantially helically around the terminal. Consequently, provided the mandrel advances continuously in one direction as it is rotated, each succeeding turn of wire wrapped on the terminal will be axially disposed relative to the preceding turn and over-wrapping of the wire will be avoided.

Preferably, the thrust means comprises a forwardly projecting step and a cam surface extending from the step generally rearwardly and around said bore in said first direction to be co-operatively engageable with said last-wrapped turn. In use, the top of this step will engage the last-wrapped turn of wire on the terminal and will follow the conformation of this turn as the mandrel is rotated so as to cause the mandrel to be axially progressed. It is preferred that adjacent turns of wrapped wire be axially compressed together in tight mutual contact and preferably, therefore, the height of the step is less than the thickness of the wire to be wrapped.

The cam surface may be so formed as to ensure that the thrust means has area contact rather than point contact with the wrapped strand. This may be done by forming the cam surface as a helix of pitch equal to the height of the step. In this way, in use, the whole of the cam surface will, when at least one turn of wire has been wrapped on the terminal, be in contact with the lastwrapped turn of wire and the wire will be wrapped generally in the form of a helix equal in pitch to that of the helically formed cam surface.

The invention will now be described, by way of example only, with reference to the accompanying drawings in which:

FIG. 1 is an isometric view of a wrapping mandrel embodying the invention;

FIG. 2 is a plan view of part of a wrapping tool embodying the invention; and

FIG. 3 is an end elevation corresponding to FIG. 2.

Referring firstly to FIG. 1, this shows a wrapping mandrel indicated generally at 10. The mandrel 10 is generally cylindrical and is formed in its forward end with a bore 12 and a wire feed aperture 14 having a slot 16 extending therefrom.

Means, not shown, is provided for rotating the mandrel 10 about the axis, indicated at 18, of the bore 12. The bore 12 extends rearwardly to receive an axially extending square cross-section terminal 22 and the mandrel 10 is rotatable about the axis 18 in a first direction indicated by the arrow 20 to wrap turns of wire onto the terminal 22 to make an electrical connection therewith.

Circumjacent the bore 12 is thrust means indicated generally at 24 and comprising a forwardly projecting step 26 and a helically formed cam surface 28 extending therefrom generally rearwardly and around the bore 12 in the direction of arrow 20. The mode of operation of the apparatus will now be described.

A length of wire 47, having one end thereof secured, is located in the wire feed aperture 14 by way of the slot 16 and the mandrel 10 is located on the terminal 22 with the terminal 22 received in the bore 12. The mandrel 10 is then rotated in the direction of arrow 20 so that the portion of the wire 47 located in the aperture 14 is carried around the terminal 22. Since one end of the wire is secured,- this rotation causes the wire to be fed through the aperture 14 and wrapped on the terminal 22. Simultaneously with the rotation of the mandrel, the cam surface 28 engages the wire wrapped on the terminal and progresses the mandrel axially along the terminal, that is in the direction of arrow 30, as will now be described in more detail.

The wire 47 is fed through the aperture 14 to an area in the region of a point on the mandrel 10 indicated at 32, and from there on to the terminal 22. The forward projection t of the thrust means 24 immediately adjacent point 32 is relatively small but increases progressively around the mandrel in a direction opposite to that of arrow 20. Thus when the mandrel is rotated in the direction of arrow 20, each portion of the wrapped wire is engaged by successively thicker portions of the thrust means 24. Provided, therefore, that the wrapped wire is securely located on the terminal 22, the mandrel 10 will be axially progressed along the terminal in the direction of arrow 30 as it is rotated in the direction of arrow 20. This process continues until the mandrel has made substantially one complete revolution and has wrapped one turn of wire on the terminal 22. At this time, the start of that turn is engaged by the top of the step 26. It follows then that during one revolution, the mandrel 10 has axially progressed in the direction of arrow 30 by an amount substantially equal to the height h of the step 26 since I is relatively small.

The mandrel has now wrapped one complete turn of wire upon the terminal 22 and is about to commence .wrapping a second turn. If the height h of the step 26 is equal to the thickness of the wire wrapped on the terminal, the second turn of wire will be just contiguous with the first turn and thus the aforedescribed process will be repeated for the second and each succeeding turn of wire. It is preferred, however, that the turns of wire be axially compressed together along the terminal 22, and this is effected by making the height h somewhat less than the thickness of the wire wrapped on the terminal.

The bore 12 and wire feed aperture 14 are located within a generally U-shaped recess, indicated generally at 34, in the end face 36 of the mandrel 10 and in use the inner wall of the recess 34 has the effect of guiding wire around a terminal located in the bore 12 and ensuring that the wire is tightly wrapped thereon. To this end, the recess 34 is so dimensioned and arranged that the corners of a terminal located in the bore 12 are spaced from the inner wall of the recess 34 by a distance approximately 15% less than the thickness of the wire wrapped on the terminal. Thus the wire is forced with a considerable load onto the terminal and it will be seen that an over-wrapped turn of wire could be crushed sufficiently to be severed and the required electrical connection would be lost.

The mandrel 10 is especially intended for use with insulated wire and the slot 16 extending from the wire feed aperture 14 has its opposite sides convergent and sharp-edged so as to nick and engage the insulation covering the wire, so that when the wire is drawn through the aperture 14, as hereinbefore described, the insulation is stripped therefrom and the wrapped wire is bare. Previously bare wire, of course, can be wrapped without stripping. Further, with certain wire, the insulation isintractably attached thereto and in such cases it is pbssible for a satisfactory wrapped joint to be made withoutstripping the wire by use of the mandrel 10, the rec es s 34 compressing the wire onto the terminal so tightly that the corners of the terminal pierce the insulation and make electrical contact with the conductive core of the wire.

The mandrel 10 has a threaded end indicated at 38 and a recessed washer 40 is secured thereon by means of a tapered, internally threaded nut 42. The washer 40 has a bore formed to engage a flat 44 on the threaded end 38 to provide an angular location for the washer. A recess 46 in the washer 40 is adapted to receive the length of wire 47 which in use is drawn through the aperture l4 and wrapped on the terminal 22. The threaded end 38 is screwed into an end of a shaft 48 which is a sliding fit in a bore in an intermediate shaft 52 and is axially retained therein by a grub screw (not shown) which also serves to locate a knurled collar 56 on the shaft 52. Rotatable on the shaft 52 is a further, hollow shaft 50 having ashoulder 54 axially adjacent the knurled collar 56. The collar 56 and shoulder 54 are formed with slots 58 and 60 and in use these slots are aligned, the wire 47 is laid therein, and the collar 56 is rotated to cut the wire 47 by a guillotining action as the slot 58 is moved relative to the slot 60. Thus a predetermined length of wire will be drawn through the aperture 14 and wrapped on the terminal 22. If the wire 47 is required to be cut to a different length, the mandrel 10 may be axially adjusted relative to the collar 56 and the shoulder 54 by slackening the grub screw. Other mandrels, having different bore sizes, may be used to accomodate terminals of different sizes.

The end of the shaft 50 which is remote from the shoulder 54 is provided with means, not shown, for engaging suitable means for rotating the mandrel and shaft assembly. Such means may comprise, for instance, a wire wrapping gun.

It will be seen from the foregoing that the invention provides means for making electrical connections 'by way of wrapped joints wherein turns of wire are wrapped on a terminal in such a way as to be serially axially disposed, so that over-wrapping is avoided.

I claim:

1. Apparatus for wrapping serially axially disposed turns of wire onto an axially extending terminal to make an electrical connection therewith, said appara tus comprising a wrapping mandrel rotatable in a first direction to wrap said Wire and having a bore formed in a forward end thereof, said bore extending rearwardly to receive the terminal, a recess defined by a wall extending at least partially about said bore to compress wrapped wire onto the terminal, said recess having a wire feed aperture adjacent said bore with said aperture terminating in a slot with the sides defining said slot being convergent with respect to one another for engaging and stripping insulation from the wire drawn through said aperture, wherein the mandrel is formed with thrust means comprising a forwarding projecting step formed ahead of the wire feed aperture in said first direction and a cam surface extending from said step generally rearwardly and around said bore in said first direction to be co-operatively engaged with a lastwrapped turn of wire on the terminal to progress the mandrel along the terminal as the mandrel is rotated to wrap the wire.

2. Apparatus according to claim 1 for wrapping wire of predetermined thickness wherein said step projects forwardly by a distance less than said predetermined thickness.

3. Apparatus according to claim 2 wherein said cam surface is formed as a helix of pitch equal to the forward projection of said step so as to conform succeeding turns of wrapped wire to said surface. 

1. Apparatus for wrapping serially axially disposed turns of wire onto an axially extending terminal to make an electrical connection therewith, said apparatus comprising a wrapping mandrel rotatable in a first direction to wrap said wire and having a bore formed in a forward end thereof, said bore extending rearwardly to receive the terminal, a recess defined by a wall extending at least partially about said bore to compress wrapped wire onto the terminal, said recess having a wire feed aperture adjacent said bore with said aperture terminating in a slot with the sides defining said slot being convergent with respect to one another for engaging and stripping insulation from the wire drawn through said aperture, wherein the mandrel is formed with thrust means comprising a forwarding projecting step formed ahead of the wire feed aperture in said first direction and a cam surface extending from said step generally rearwardly and around said bore in said first direction to be co-operatively engaged with a last-wrapped turn of wire on the terminal to progress the mandrel along the terminal as the mandrel is rotated to wrap the wire.
 2. Apparatus according to claim 1 for wrapping wire of predetermined thickness wherein said step projects forwardly by a distance less than said predetermined thickness.
 3. Apparatus according to claim 2 wherein said cam surface is formed as a helix of pitch equal to the forward projection of said step so as to conform succeeding turns of wrapped wire to said surface. 